Fig 5 Shows Cardiovascular Stent Following Laser Cutting
Fig 6 - 7 Shows Cardiovascular Stent after Electropolishing with rounded edge profile
Passivation & Desmuting
Following drilling, grinding, punching and fabrication often the surface has not had sufficient time to create its own natural passive layer before the part is to be put in to service. It is therefore advisable to have a simple passivation step to be carried out. This may be done with a relatively short immersion in Willowchem 70 or 71.
In special applications used for high purity fittings and conveyance lines high levels of passivation is required for full protection and reduce any contamination to the conveyance media. These processes use heated and high concentration passivation products and are measured by ratio’s of iron oxide to chromium oxide through Auger spectrometry. This process should only be carried out by experience specialist companies. Further information may be obtained from a local Willowchem Technology partner.
Whilst electropolishing oxygen is liberated at the anode (Work piece) and therefore when removing from the process the components is almost at its full potential passivity. However, some complex metal salts are formed in the process that do not readily rinse in water. These metal salts can cause slight contamination and complications in some particular applications and also create staining. It is therefore advisable to carry out a simple immersion in a desmuting solution such as Willowchem 71.
Following any of the passivation or desmuting processing, the components should be fully rinsed in clean freash water. It is often advisable to use a final hot water rinse with a a low conductivity (i.e deionised) which assist with flash drying and reduces water staining.